1. Field of the Invention
This invention relates to a multi-function air driven screwdriver, especially designed to perform the hole drilling, thread tapping and bolt tightening. It eliminates the attachment of the clutch, makes the tool shorter and lighter, and becomes a practical machine tool.
2. Description of the Prior Art
On most prior art of semi-auto air-driven screwdrivers, pressing action is utilized (pressing down or releasing) to the control the start or stop of inner motor section and the drive comes from the active gear assembly but not moveable. The gear disk will move the upper clutch and the lower clutch and the torque magnitude are controlled by the clamping action of the torque spring. When the torque reaches at a specified level, the motor section and the gear, assembly begins to rotate, however, the lower clutch and the screwdriver tip remain motionless. When the pressing is released, the motor section and the gear assembly stop. This is the action to complete bolt tightening. In this design, the motor section is a must the driving mechanism is conceivably complicated.
In this bolt tightening process, from the start of the motor section to the stop of operation, in which, the preset torque, the motor inertia, the control over the frequency of motor repeated jumping and the torque applied to tighten the bolt are critical to the precision and quality of bolt tightening. However, the manual control and operation of the air-driven screwdriver can never be maintained at a specified standard, so the high quality of tightening bolt is too hard to keep.
In the prior art of the air-driven screwdriver, the torque spring which is used to preset the torque, is mounted between the screwdriver tip and the motor section and passing the sleeve and the connecting rod and the motor inertia is employed to control the jumping frequency of the motor so as to stop the motor running. In case it is necessary to change the preset torque, it has to disassemble the whole screwdriver in order to change the torque spring, a time-consuming operation. If the change frequency of required torque is high, it is an extreme bothering to the operator. In adjusting the preset torque, variation occurs frequent in clutch jumping frequency and motor stop timing which leads to varying preset torque. For this point, the prior art of the air-driven screwdriver will never succeed.